Printer drive with page record feed

ABSTRACT

A printer drive mechanism for a printer including a cylindrical platen and page record mechanism coaxially mounted on the platen shaft. A gear train connects the platen to the page record feed mechanism allowing synchronous but independent rotation of the platen and the page record feed mechanism, with the page record feed mechanism rotating at a slower rate than the platen. A stepping motor is used to rotate the platen, and printing occurs after each step of the motor thereby preventing the printed dot from blurring due to platen rotation or page record advancement.

United States Patent Feder Mar. 7, 1972 [54] PRINTER DRIVE WITH PAGERECORD FEED [72] Inventor: Alvin Feder, Skokie, ll].

[73] Assignee: Motorola, Inc, Franklin Park, 111.

[22] Filed: Feb. 13, 1970 211 Appl. 140.: 11,258

[52] U.S.Cl. ..346/l0l, 101/93 C, 178/25 [51] Int. Cl. ..B4lj 11/24,8413' 11/38 [58] Field ofSearch ..101/93 C, 93 R, 93 MN;

346/101; 178/25, 32 561 References Cited UNITED STATES PATENTS 1,848,8623/1932 Young ..346/ l 01 X 3 ,409,904 1 1/1968 Maiershofer... ..346/ 1012,934,974 5/1960 Schoepe ....l92/47 X 2,909,996 10/1959 Fitch ..l01/93 C1,958,885 5/1934 Carlisle .L ..346/l01 Chilberg et a1. .346] 101 AmadaHell Alden Young ..346/ l 01 Primary Examiner-J. Reed FisherAttorney-Mueller & Aichele ABSTRACT A printer drive mechanism for aprinter including a cylindrical platen and page record mechanismcoaxially mounted on the platen shaft. A gear train connects the platento the page record feed mechanism allowing synchronous but independentrotation of the platen and the page record feed mechanism, with the pagerecord feed mechanism rotating at a slower rate than the platen. Astepping motor is used to rotate the platen, and printing occurs aftereach step of the motor thereby preventing the printed dot from blurringdue to platen rotation or page record advancement.

9 Claims, 5 Drawing Figures PATENTEDIMR "/1912 3,647. 356

SHEET 1 UF 2 FIG. 1'

FIG. 3

Inventor ALVIN FEDER ATTYS.

PATENTEDMAR 7 I972 SHEET 2 BF 2 Ga a Inventor ALVIN FEDER W E Rau wATTYSh PRINTER DRIVE WITH PAGE RECORD FEED BACKGROUND OF THE INVENTIONMechanical drive mechanisms in printers require a platen for printingand a page record drive mechanism to drive the paper through theprinter. Print hammers strike the paper against the platen to print asymbol. Prior printers have mounted the paper feed wheels coaxially withthe platen, however, the feed wheels were rotatably secured to theprinter chassis. A ratchet mechanism, actuated by an appropriate signal,turned the page record drive mechanism thereby advancing the paper. Boththe mechanical mounting of the drive mechanism and the ratchet mechanismwere complex, expensive, and unsuitable for use in a mobile environment.Lack of synchronization between the platen, printer hammers, and pagerecord drive mechanisms caused overtyping and inconsistent spacingbetween printed lines.

SUMMARY OF THE INVENTION It is therefore an object of this invention toprovide a simplified printer drive mechanism for use in a mobileprinter.

Another object of this invention is to provide a printer drive mechanismwherein no ratchet mechanism is required to advance the page record.

Yet another object of this invention is to provide a printer drivemechanism wherein the page record feed means is precisely synchronizedwith the platen rotation and printer hammer operation.

In practicing this invention a printer drive mechanism is providedwherein a platen shaft having a helical platen vane thereon is rotatablysecured to the printer chassis. Page record feed wheels are rotatablymounted on a journaled portion of the platen shaft, adjacent each end ofthe helical platen vane. A stepping motor is secured to the printerchassis adjacent the platen shaft and coupled to the platen shaftthrough a pair of gear wheels. The other end of the platen shaft iscoupled through a series of reducing gears to a gear shaft which has twogears thereon. The two gears on the gear shaft are coupled to gear teethon the page record feed mechanism. Rotation of the platen shaft by thestepping motor causes the page record feed mechanism to rotate in thesame direction as the platen shaft but at a slower rate of rotation.Tension wheels mounted to springs secured to the printer chassis, bearagainst the page record feed mechanism causing the page record to bealigned parallel to the platen shaft. Pizoelectric printer hammers areselectively energized to strike against the page record and platen vanecausing a dot to appear on the page record. The piezoelectric printerhammers are actuated after the motor has stepped and while the platenvane and page record feed mechanism are stopped so that the printed dotwill not be blurred.

In a second embodiment the reducing gears couple the platen shaft to thepage record feed mechanism such that the page record feed mechanism isincremently rotated once for each full revolution of the platen shaft.Allowing rotation of the page record feed wheels once after each platenrotation simplifies the gearing mechanism and positioning of thepiezoelectric printer hammers. The simplified gearing allows the use ofthe lower torque stepping motor.

A spring biased knurled thumbwheel located on the printer front panel,allows manual advancement of the page record. Pushing the thumbwheelupward will also depress the thumbwheel and cause it to bear against asecond wheel located at the end of a gear shaft which is coupled to thepage record feed mechanism. The gear shaft is normally rotated by a geartrain coupled to the platen shaft. Rotation of the thumbwheel disengagesa one-way slip clutch coupling the gear shaft and the drive train,thereby allowing the gear shaft and page record feed mechanism to berotated independent of the platen shaft and gear train.

The invention is illustrated in the drawings of which:

FIG. 1 is a perspective drawing of the printer drive mechanism;

FIG. 2 is a plan view of the printer drive mechanism of the invention;

FIG. 3 is a cutaway drawing showing a page record drive mechanism;

FIG. 4 is a perspective drawing of another embodiment of the invention;

FIG. 5 is a perspective drawing ofa portion of the gear train shown inFIG. 4.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2 there is shown a printerdrive mechanism incorporating the features of this invention. Theprinter drive mechanism has a rotary platen having a platen shaft 21 anda raised helical portion or vane 22. Adjacent to the raised helicalportion 22 there is a paper drive mechanism 27 and 28 rotatably mountedon a journaled portion of the platen shaft 21. Bearings 29 and 30rotatably mount platen shaft 21 on chassis mounting bracket 31. Steppingmotor 33, coupled to the platen shaft 21 through gears 34 and 35, drivesthe platen 20 in the direction of arrow 36. In this embodiment theplaten is rotated at I66 revolutions per minute, with 48 steps perrevolution. Platen gear 38 mounted at the end of the platen shaft 21drives a gear train consisting of gears 39, 40 and 41 which arerotatably mounted to chassis mounting bracket 31. Gear 41 is connectedthrough a one-way clutch 42 to gear shaft 43. Gear shaft 43 is rotatablymounted in chassis mounting bracket 31 by bearings 45 and 46. Gears 49and 50 mounted on gear shaft 43 engage gears 51 and 52 of page recordfeed mechanisms 27 and 28 causing the page record feed mechanisms torotate. The purpose of the gear train is to allow the page record feedmechanisms 27 and 28 to rotate at a speed slower than the speed ofplaten 20 yet retain a synchronization between the rotation of theplaten 20 and the rotation of page record feed mechanisms 27 and 28. Inthis embodiment the page record feed mechanisms 27 and 28 rotate at aspeed of 1.57 revolutions per minute, with 48 stops per revolution. Thegear train produces a speed reduction of 105 to l.

Referring to FIG. 3 the page record feed mechanism 27 includes acylindrical metal portion 53 having a hollow center 48. The cylindricalmetal portion 53 is inserted into the center opening of a cylinder 54,preferably made of a plastic material such as polyurethane. Cylinder 54bears against the paper, feeding it through the printer mechanism. Theother end of metal cylinder 53 is inserted into a center opening in pagerecord drive gear 52. Page record drive gear 52 and cylinder 54 areseparated by ridge 55 on metal cylinder 53. Ballbearings 56 and 57 areinserted in metal cylinder 53 to allow the page record feed mechanism 27to rotate on platen shaft 21.

Pressure rollers 58 and 59 (FIG. 1) rotatably mounted on spring brackets60 and 61, bear against paper drive mechanisms 27 and 28 causing theink-impregnated paper 62 to move upward in front of platen 20.Piezoelectric printer hammers 63, when actuated by a proper electricsignal will strike against the ink-impregnated paper 62 and the platenhelix 22 causing a dot to appear on the paper.

In operation stepping motor 33 rotates, turning platen 20 at 166revolutions per minute, wheel 64 secured to gear 35 has a magnet 65thereon. Magnetic relay 66 located adjacent platen shaft 21 will beenergized once every revolution of platen shaft 21 when magnet 65 passesmagnetic relay 66. The signal produced when magnetic relay 66 isenergized is used to synchronize the rotation of the platen 20 andoperation of the piezoelectric printer hammers 63. Stepping motor 33stops 48 times in each revolution, causing platen 20 and the page recordfeed mechanisms 27 and 28 to also stop. While stopped electronic signalsactuate piezoelectric hammers 63 causing them to strike theink-impregnated paper 62 against platen helix 22, producing a dot. Bystopping rotation of the platen 20 and page record feed mechanisms 27and 28 each time a dot is printed, no blurring of the dot will occur. Aline of dots can be printed for each rotation of platen 20. As the pagerecord feed mechanisms 27 and 28 advance the paper slightly for eachrevolution of platen 20, a line of dots printed in a single revolutionof platen 20 would be slightly skewed on the page record. To eliminatethis problem piezoelectric hammers 63 are skewed slightly with those atthe left being lower than those at the right. To provide a space betweenprinted lines plate 20 is allowed to rotate an approptiate number oftimes without actuating any of the piezoelectric printer hammers 63,thereby allowing page record feed mechanisms 27 and 28 to advance thepage record.

Referring to FIGS. 4 and 5 there is shown a second embodiment of aprinter drive mechanism incorporating the features of this invention.Gear wheel 74 mounted at the end of platen shaft 21 has a single geartooth recess 75 in the peripheral edge. An axially protruding tab 80,secured to face 81 of gear wheel 74 will bear against secondary geartooth 82 causing gear wheel 76 to rotate and position primary gear tooth83 on gear wheel 76 to allow engagement with gear tooth recess 75 ongear wheel 74. The proximity of gear wheels 74 and 76 prevents gearwheel 76 from turning freely until tab 80 bears against secondary geartooth 82 and a primary gear tooth 72 on gear wheel 76 is in alignmentwith gear tooth recess 75 in gear wheel 74. Gear wheel 74 drives thegear train consisting of gears 76, 77 and 78, which are rotatablymounted to chassis mounting bracket 31. As in the previous embodiment(FIG. 2) gear 78 (gear 41 in FIG; 2) is connected through a one-wayclutch 42 to gear shaft 43.

When platen has completed one full revolution, gear tooth recess 75 ingear wheel 74 will engage and rotate gear 76. This rotation will betransferred from gear 76 through gears 77 and 78, gear shaft 43, andshaft gears 49 and 50 to paper drive mechanisms 27 and 28. As a line ofdots may be printed in each rotation of platen 20, without the pagerecord advancing as the line is printed, the piezoelectric printerhammers 63 can be assembled parallel to platen 20 and not skewed asshown in the previous embodiment. Since skewing of the piezoelectricprinter hammers 63 requires adjustment to precise tolerances, the use ofa drive mechanism which advances the page record, after each line ofdots, simplifies installation and maintenance of the printer drivemechanism.

With the gears coupled to the platen shaft 21 only once in eachrevolution there is less drag on platen 20 and therefore a lighter loadon stepping motor 33. With the lighter load on stepping motor 33, alower torque and less expensive stepping motor may be used in theprinter drive mechanism.

In order to manually advance the page record, a spring biased thumbwheel68 (FIG. 1) is provided which is mounted on the printer front panel 69.To advance the paper the thumbwheel 68 is pushed upward and rotated inthe direction of arrow 70. This upward pushing movement also depressesthe thumbwheel 68 and engages, in frictional drive, wheel 71 fastened onan extension of gear shaft 43. Rotation of thumbwheel 68 causes rotationof wheel 71 and gear shaft 43. One-way clutch 42 mounted on gear shaft43 allows gear shaft 43 to rotate independent of gear 41 (or gear 78 inFIG. 4). The rotation of gear shaft 43 rotates shaft gears 49 and 50causing page record feed mechanisms 27 and 28 to rotate, therebyadvancing the page record.

As can be seen, a simplified printer drive mechanism has been providedwhich is capable of operation in shock and vibrational environment. Useof a coaxially mounted platen and page record feed mechanismsynchronously driven by a motor and gear train eliminates the need forcomplex ratchet or escapement mechanisms and provides a simplified drivemechanism less susceptible to improper operation, shock and vibration.

lclaim:

l. A mechanical drive mechanism for a symbol printing page recordprinter including in combination, an elongated rotatable platen, pagerecord feed means rotatably mounted coaxially on said platen adjacenteach end thereof, mounting means for rotatably mounting said platen tothe symbol printing page record printer, a stepping motor coupled tosaid platen for incrementally rotating said platen at a first rate ofrotation, first gear means coupling said page record feed means to saidplaten, said first gear means including a gear shaft rotatably mountedto said mounting means, first and second gear wheels secured to saidshaft and in operative association with said page record feed means,clutch means secured to said shaft, and transfer gear means rotatablymounted to said mounting means and in operative association with saidplaten and said clutch means for transferring said platen rotation tosaid page record feed means by way of said clutch means andsynchronously, incrementally rotating said record feed means at a secondrate of rotation slower than said first rate of rotation, and manualpage record feed means including a first wheel secured to an end of saidgear shaft, a thumbwheel and biasing mounting means therefor for holdingsaid thumbwheel a first position spaced from said first wheel, saidthumbwheel being movable to a second position in operative associationwith said first wheel so that rotation of said thumbwheel causes saidfirst wheel, said gear shaft, and said first and second gear wheels torotate by way of said clutch means independently of said transfer gearmeans, whereby said page record feed means is rotated independently ofthe rotation of said platen.

2. The mechanical drive mechanism of claim 1 wherein said page recordfeed means includes, a cylindrical shaped portion, a gear wheel havinggear teeth in the peripheral edge secured to one end of said cylindricalshaped portion, a hole cut through said gear wheel and cylindricalportion along the axis of said cylindrical portion, and bearing meanssecured to the walls of said hole for rotatably mounting said pagerecord feed means on said platen shaft.

3. The mechanical drive mechanism ofclaim 1 wherein said platenincludes, a cylindrical platen shaft and a raised helical platen vane,said platen shaft extending through and rotatably supporting said pagerecord feed means on each side of said helical platen vane, said platenshaft being rotatably mounted on said mounting means, second gear meansat an end of said platen shaft in operative association with said firstgear means, and third gear means at the other end of said platen shaftin operative association with said stepping motor.

4. The mechanical drive mechanism of claim 3 wherein said second gearmeans is a gear wheel having a single gear tooth in the peripheral edge.

5. The mechanical drive mechanism of claim 3 wherein said second gearmeans is a gear wheel having a plurality of gear teeth in the peripheraledge.

6. The mechanical drive mechanism of claim 3 wherein said transfer gearmeans includes a plurality of gear wheels coupling said second gearmeans on said platen shaft to said gear shaft to incrementally rotatesaid page record feed means when said platen is rotated.

7. The mechanical drive mechanism ofclaim 6 wherein said transfer gearmeans includes, a third gear wheel having gear teeth on the peripheraledge thereof coupled to said clutch means, a fourth gear wheel rotatablysecured to said mounting means having first and second gears thereon, afifth gear wheel rotatably secured to said mounting means having thirdand fourth gears thereon, said third gear in operative association withwith said second gear on the fourth gear wheel, said fourth gear inoperative association with said second gear means on said platen shaft,said gear wheels and gear shaft cooperating to incrementally rotate saidpage record feed means when said platen is rotated.

8. The mechanical drive mechanism ofclaim 6 wherein said transfer gearmeans includes, a third gear wheel having gear teeth in the peripheraledge thereof coupled to said clutch means, fourth and fifth gear wheelshaving gear teeth in the peripheral edge thereof rotatably secured tosaid mounting means, said fourth gear in operative association with saidsecond gear means on said platen shaft, said gear wheels and gear shaftcooperating to incrementally rotate said page record means when saidplaten is rotated.

9. The mechanical drive mechanism of claim 6 wherein said clutch meansis a one-way clutch allowing rotation of said gear shaft in only onedirection of rotation.

1. A mechanical drive mechanism for a symbol printing page recordprinter including in combination, an elongated rotatable platen, pagerecord feed means rotatably mounted coaxially on said platen adjacenteach end thereof, mounting means for rotatably mounting said platen tothe symbol printing page record printer, a stepping motor coupled tosaid platen for incrementally rotating said platen at a first rate ofrotation, first gear means coupling said page record feed means to saidplaten, said first gear means including a gear shaft rotatably mountedto said mounting means, first and second gear wheels secured to saidshaft and in operative association with said page record feed means,clutch means secured to said shaft, and transfer gear means rotatablymounted to said mounting means and in operative association with saidplaten and said clutch means for transferring said platen rotation tosaid page record feed means by way of said clutch means andsynchronously, incrementally rotating said record feed means at a secondrate of rotation slower than said first rate of rotation, and manualpage record feed means including a first wheel secured to an end of saidgear shaft, a thumbwheel and biasing mounting means therefor for holdingsaid thumbwheel a first position spaced from said first wheel, saidthumbwheel being movable to a second position in operative associationwith said first wheel so that rotation of said thumbwheel causes saidfirst wheel, said gear shaft, and said first and second gear wheels torotate by way of said clutch means independently of said transfer gearmeans, whereby said page record feed means is rotated independently ofthe rotation of said platen.
 2. The mechanical drive mechanism of claim1 wherein said page record feed means includes, a cylindrical shapedportion, a gear wheel having gear teeth in the peripheral edge securedto one end of said cylindrical shaped portion, a hole cut through saidgear wheel and cylindrical portion along the axis of said cylindricalportion, and bearing means secured to the walls of said hole forrotatably mounting said page record feed means on said platen shaft. 3.The mechanical drive mechanism of claim 1 wherein said platen includes,a cylindrical platen shaft and a raised helical platen vane, said platenshaft extending through and rotatably supporting said page record feedmeans on each side of said helical platen vane, said platen shaft beingrotatably mounted on said mounting means, second gear means at an end ofsaid platen shaft in operative association with said first gear means,and third gear means at the other end of said platen shaft in operativeassociation with said stepping motor.
 4. The mechanical drive mechanismof claim 3 wherein said second gear means is a gear wheel having asingle gear tooth in the peripheral edge.
 5. The mechanical drivemechAnism of claim 3 wherein said second gear means is a gear wheelhaving a plurality of gear teeth in the peripheral edge.
 6. Themechanical drive mechanism of claim 3 wherein said transfer gear meansincludes a plurality of gear wheels coupling said second gear means onsaid platen shaft to said gear shaft to incrementally rotate said pagerecord feed means when said platen is rotated.
 7. The mechanical drivemechanism of claim 6 wherein said transfer gear means includes, a thirdgear wheel having gear teeth on the peripheral edge thereof coupled tosaid clutch means, a fourth gear wheel rotatably secured to saidmounting means having first and second gears thereon, a fifth gear wheelrotatably secured to said mounting means having third and fourth gearsthereon, said third gear in operative association with with said secondgear on the fourth gear wheel, said fourth gear in operative associationwith said second gear means on said platen shaft, said gear wheels andgear shaft cooperating to incrementally rotate said page record feedmeans when said platen is rotated.
 8. The mechanical drive mechanism ofclaim 6 wherein said transfer gear means includes, a third gear wheelhaving gear teeth in the peripheral edge thereof coupled to said clutchmeans, fourth and fifth gear wheels having gear teeth in the peripheraledge thereof rotatably secured to said mounting means, said fourth gearin operative association with said second gear means on said platenshaft, said gear wheels and gear shaft cooperating to incrementallyrotate said page record means when said platen is rotated.
 9. Themechanical drive mechanism of claim 6 wherein said clutch means is aone-way clutch allowing rotation of said gear shaft in only onedirection of rotation.